Hi @Anonymous, first of all thanks for post.
i think the best way to do this is using a schedule to get all documents, look at example below:

Detaileds Steps:
1 - Use an schedule trigger with 1 day interval
2 - Use the action - SharePoint - Get file properties only
Put your Site and Document Libary name
3- Use an foreach and put values as result
4- Use an advanced condiction to verify if the actual date is greater than document created date + 7
This is the condiction code, in red are the days to add, change if you need:
@greater(utcNow('yyyyMMdd'), formatDateTime(adddays(item()?['Created'],7),'yyyyMMdd'))
5- If the condiction is yes, the document is older than 7 days
6- Use the action - SharePoint - Delete Item
Hope this helps.
Best Regards,
Gustavo Moraes